A lithium ion secondary battery package includes a specific number of stacked battery cell packs each incorporating a battery cell (single cell) that are accommodated in a housing. Inside the housing, the battery cell packs are electrically connected in series or in parallel with one another. Specifically, the battery cell packs are connected in series or in parallel by spot-welding electrode tabs of the individual battery cell packs. Desired power performance is obtained by connecting the battery cell packs in this way.
As the electrode tabs are connected as mentioned above, there exist electrode tabs which should be spot-welded as well as electrode tabs which should not be spot-welded. Thus, according to Japanese Patent No. 4462386-B2, electrode tabs of battery cell packs are initially formed in a large size and subsequently cut into specific shapes so that only particular ones of the electrode tabs can be connected.